The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Known internal combustion engines may be configured with air compressors that boost intake air to increase engine power over that achievable using natural aspiration. Known air compressors include superchargers and turbochargers. A supercharger is a mechanically-driven device that employs power originating from an engine crankshaft or another source, e.g., an electric motor to drive an intake air compressor. A turbocharger is a turbine-driven device that employs power originating from exhaust gas flow to drive an intake air compressor. Both compression-ignition (CI) engines and spark-ignition (SI) engines can employ air compressors to boost intake airflow.
Employing a turbocharger unit in an engine exhaust system can lead to increased exhaust pressure under some operating conditions, thus potentially affecting engine performance and service life of engine and exhaust components. Engine performance may be related to engine pumping, internal EGR flow, external EGR flow, cylinder scavenging, and other or related performance parameters. Affected engine and exhaust components may include seals in the turbocharger, seals in engine exhaust valves, and other or related components such as downstream exhaust emissions components. Low exhaust pressure may result in insufficient pressure difference across an EGR valve to provide sufficient flow of recirculated exhaust gas into an intake manifold. Excessive exhaust pressure can lead to high exhaust temperature, resulting in overheating of an exhaust valve and a turbine element. Furthermore, excessive exhaust pressure can reduce service life of a turbocharger seal, with accompanying occurrence of oil leakage into the exhaust system.